Quote:
Originally Posted by blink138
hi slawomir and thanks for a reply
usually i cannot get more than a couple of minutes from my dslr at iso 800 or 1000 before sturation on histogram, however just testing my ccd the histo doesnt seem to move hardly at all to the right even after 5 or 6 minutes!
i have been reading a bit about the offset and gain but i do not know wether or not it will make any difference
pat
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Hi Pat,
5-6 minutes is a relatively short exposure for an astro CCD-based camera, unless you aim it at bright objects such as the Orion Nebula or Carina Nebula.
I am it sure whether you are aware of it or not, but astro images need careful stretching to bring up faint detail while at the same time keeping stars from reaching saturation point as much as possible. NASA's FITS Liberator (free software) is quite good at automatic stretching of your images. I prefer using PixInsight for entire processing of my images.
So usually, a histogram of an image straight from the camera will look underexposed on a computer screen and predominantly populated on the left side (majority of pixels having low ADU values).
EDIT: This might help- you can go straight to page 13:
https://www.spacetelescope.org/stati.../userguide.pdf